1. Field of the Invention
This invention pertains to the beverage filling art and more particularly relates to filling pressurized or carbonated beverages into containers such as lightweight cans, jars, beer mugs or the like.
2. Description of Prior Art
Fillers for filling carbonated beverages such as beer or soft drinks into cans are well known in the art. Most of the prior art fillers discharge the beverage into containers while the beverage is under its super-atmospheric supply pressure of between about 40-15 psi gauge. Thus, the filling valves are provided with resilient can lip seals which engage the upper edge of the cans, and each can must be supported on a can lift table which forces the can upwardly against the seal with a force at least equal to the beverage supply pressure multiplied by the cross sectional area of the container. Such forces are on the order of about 230 pounds when the beverage pressure is 40 psi and a standard 2 11/16th diameter beverage can is being filled. Because of this high sealing pressure, the life of the lip seal is very short, and seal wear which occurs before final seal failure varies the volume of beverage being filled into the cans by leakage past the seal and by inconsistent amounts of bowing of the end of the cans. A further disadvantage of this type of prior art pressure filling apparatus is that the wall thickness of the cans must be relatively thick to withstand the high sealing pressure and thus the cost of the containers are unnecessarily high. Another disadvantage is that the carbonated liquid which is directed into the container is directed in and runs down the walls of the containers at relatively high speed causing a "scrubbing" action which tends to release the carbon dioxide from the liquid providing objectionable foaming of the liquid. Also, air within the empty containers is discharged into the headspace of the supply tank resulting in an undesirable mixture of air and carbon dioxide in the headspace of the tank. Furthermore, each filling valve must be provided with a snifter valve to bleed air and carbon dioxide from the container headspace before the container is released from the lip seal.
Carbonated beverage filling machines which use a "bottom filling" concept have been proposed previously as shown by the disclosure of U.S. Pat. No. 2,144,628 to Hothersall for example. In the machine disclosed in this patent, a measuring cylinder which includes a foot valve at its lower end is arranged to be filled with a carbonated beverage, such as beer, from a reservoir. The cylinder is then lowered into a container to the bottom thereof and the foot valve is opened to allow the beverage to flow into the container. The cylinder is raised as the beverage flows out until the container is filled as the cylinder is raised out of the container. In order to prevent the foaming of the beverage during filling, the measuring cylinder is vented to the atmosphere. However, such a provision causes difficulties in providing an exact predetermined amount of beverage during each filling cycle and also results in the possibility of spilling a portion of the beverage out of the measuring cylinder through the vent passage.